ONE PIECE RING GEAR-PARK BRAKE DRUM
A component for transmitting torque between a gear unit and a shaft includes a ring gear portion, a park brake drum portion formed integrally with the ring gear portion, a disc portion formed integrally with the park brake drum portion, and a hub portion formed integrally with the disc portion.
1. Field of the Invention
This invention relates generally to metal forming and, in particular, to an integrated ring gear-parking brake drum produced in one piece from a cold-formed preform. Helical gear teeth are formed on a ring gear portion of the product and spline teeth on a hub portion.
2. Description of the Prior Art
The kinematic arrangement of an automatic transmission for a rear wheel drive motor vehicle may include a Ravigneaux gearset, whose components include two sun gears, a ring gear surrounding the sun gears and two sets of planetary pinions. The pinions of a first set mesh with a first sun gear and the ring gear, the pinions of the second set mesh with a second sun gear and the pinions of the first set. The transmission output torque is carried by the ring gear, transmitted axially by a parking drum to a radial disc and transmitted radially to a sleeve or hub, which is connected by a spline to the transmission output shaft and is connected to the radial member.
The ring gear is formed with internal, helical gear teeth. The parking drum is formed with external spline teeth, which are engaged by a park pawl, secured to the transmission case for preventing the vehicle from moving inadvertently when the wheel brakes are disengaged.
According to a current manufacturing process the ring gear, the park brake drum, and the radial disc and its hub are formed as separate components, each produced to precision dimensions. The helical ring gear is laser welded to the park brake drum. The output shaft hub-radial disc is attached to the park brake drum using a spline and snap ring.
The park brake drum, output shaft hub and radial disc are formed extensively to carry principally torsion load in the application. Each component is machined to tight tolerance. The ring gear, however, cannot be machined directly into the parking drum because the ring gear must be broached, requiring a long broach bar to pass completely through the ring gear.
A need exists in the industry for this combination of separate components to be formed integrally, i.e., in one component without need for bonding, welding or mechanical connections among the components, yet providing a mechanical connection to a transmission shaft.
SUMMARY OF THE INVENTIONA component for transmitting torque between a gear unit and a shaft includes a ring gear portion, a park brake drum portion formed integrally with the ring gear portion, a disc portion formed integrally with the park brake drum portion, and a hub portion formed integrally with the disc portion.
The one-piece ring gear-park brake drum is produced at lower cost than the multiple-piece assembly and requires no mechanical connections, welds or bonded connections. Complexity during assembly is greatly reduced compared to the three -piece assembly. Warranty costs are reduced due to few parts and no inter-part connections, which reduce opportunity for in-service component failure. The component is inherently more rigid, lighter and better balanced than a multi-piece assembly.
The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art.
The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which:
Referring now to the drawings,
The flow forming procedure illustrated in
The outer surface 18 of preform 14 is flow formed into a cylinder 40 by contact pressure between preform 14 and the rollers 30 and movement of the rollers over the mandrel 24 and preform. The inner surface 16 of preform 14 is flow formed due to contact pressure between preform 14 and the outer surface of the mandrel 24. The material of the cylindrical wall of the preform 14 flows axially and radially with respect to axis 32, as the rollers 30 and roller feed 36 move as a unit along axis 32 and angularly and radially with respect to the axis.
Alternately, the outer surface 18 of preform 14 is not a uniform circular cylinder but instead is a cylinder 41 formed with exterior features, such as changes in its wall thickness due to the material of the cylindrical wall of the preform flowing axially and radially with respect to axis 32 as the rollers 30 move both axially about axis 32 and radially with respect to axis 32, as
Similarly, the outer surface 26 of the mandrel 24 may be other than a circular cylinder. For example, the outer surface 26 of the mandrel 24 may be formed with gear teeth extending along at least a portion of the length the length of the mandrel, or the outer surface of the mandrel 24 may be formed with cam ramps for the outer race of a one-way clutch, the cam ramps being arranged about axis 32 and extending along at least a portion of the length of the mandrel. In these instances, the inner surface 16 of the perform cylinder 14 will be flow formed either with helical gear teeth or cam ramps.
As
An alternate process for forming a preform cylinder, called in-die forming, is described with reference to
Plate 50 is placed over a solid die 58 centered about axis 32. Die 58 includes a shoulder 62 having an internal radius 64, and a body 66 having an outer surface 68. A draw ring 70 contacting the upper surface 54 of plate 50 is forced by a hydraulic press (not shown) downward in several progressive stages causing the plate to conform to the surface of shoulder 62, radius 64 and surface 68.
As
When plate 50 is formed into the shape of the preform cylinder 14 shown below axis 32 in
The outer surface of preform 14 is flow formed by contact pressure between preform cylinder 14 and rollers 30 and by movement of the rollers over the mandrel 24 and the preform. The inner surface of preform cylinder 14 is flow formed due to contact pressure, which forces the preform into contact with the outer surface 68 of mandrel 24. The material of the cylindrical wall of the preform 14 flows axially and radially with respect to axis 32 as the rollers 30 move axially along the axis 32, circumferentially about the axis and radially with respect to the axis.
Preferably, the outer surface 26 of the mandrel 24 is formed with a circular cylinder 71, splines or gear teeth 72 for a planetary gearset of an automatic transmission, or cam ramps 73, such as those that are formed on the inner surface of a one-way clutch race. As flow forming step is performed, the perform 14 attains the shape of cylinder 40, 41 and the inner surface of perform 14 conforms to the shape on the outer surface 68 of mandrel 24. In this way either certain gear teeth, splines 72, cam ramps 73 or a circular cylinder 21 are flow formed on the outer surface 68 of mandrel 24.
After the flow forming step is executed, the flow formed cylinder 40, 41 will have the shape illustrated in
The flow formed cylinder 40, 41 is then cut transversely with respect to axis 32 into multiple segments or ring blanks 76 using either a laser cutting technique or a concentrated jet of pressurized water, as described with reference to
An alternate method for cold forming a clutch race 90 by extruding the cam surface net-shape in die tooling is described with reference to
Each circular cylindrical segment 42 is spheroidize annealed and coated with a standard phosphate/soap coating, which actions are conventional in metal forming operations.
As
After forming the cam ramp surfaces 74 on the inner surface of the segment 42, the outer surface 18 of the segment is ground to within a tight tolerance and the inner surface 16 has a series of cam ramp surfaces 74 arranged angularly about axis 96 and formed to near net shape. The clutch race 90 is thereafter finish machined, thermally processed and coated.
An alternate method for cold forming a ring gear 100 by extruding the gear teeth net-shape in die tooling is described with reference to
Each circular cylindrical segment 42 is spheroidize annealed and coated with a standard phosphate/soap coating, which actions are conventional in metal forming operations.
As
After forming the gear teeth 84 on the inner surface of the segment 42, the outer surface 18 of the segment is ground to within a tight tolerance and the inner surface has a gear teeth arranged angularly about central axis 96 and formed to near net shape. The ring gear 100 is thereafter finish machined, thermally processed and coated.
Referring to
Transmission output torque is transmitted to the transmission output shaft 140 by a ring gear-brake drum 130, which is formed integrally, i.e., in one component without need for bonding, welding or a mechanical connection between or among components. The ring gear-brake drum 130 includes the ring gear 124, a park brake drum 132, a radial disc 134, and a sleeve hub 136. Transmission output torque carried by the ring gear 124 is transmitted axially by the park brake drum 132 to the radial disc 134, which carries the torque to the sleeve hub 136, which is connected by a spline 138 to the transmission output shaft 140. The ring gear 124 is formed with internal, helical gear teeth 84. The parking drum 132 is formed with external teeth 142, which are engaged by a park pawl, secured to the transmission case for preventing the vehicle from moving inadvertently when the wheel brakes are disengaged.
To avoid the necessity of producing and interconnecting multiple separate components, the integrated ring gear-park brake drum 130 is produced, as described with reference to
The hub portion 136 is formed by extruding or drawing the central portion of plate 50 through an external die 156 and passing an internal die 158 through hole 152, thereby cold forming the preform 160 shown in
Preform 160 is cold formed progressively in successive steps to the shapes shown in
When preform 160 is formed into the shape of a cylindrical preform 170, either with walls of uniform or varied thickness, dies 158 and 164 are removed from the preform and a flow forming mandrel 172 is inserted into the cylindrical preform. The tailstock 28 is used to clamp preform 170 to the mandrel 172. Then rollers 30 are forced into contact with the outer surface 174 of preform 170. Each roller 30 rotates about its respective axis 34 and translates along axis 154.
The outer surface 174 is flow formed by contact pressure between preform 170 and rollers 30 and by movement of the rollers over the preform.
The inner surface 176 of preform 170 is flow formed due to contact pressure between preform 170 and mandrel 172, which contact pressure forces the preform into contact with the outer surface 180 of mandrel 172.
The outer surface 180 of mandrel 172 is formed with external gear teeth 182. In this way, helical gear teeth 84, shown in
In a separate operation, the cup shaped preform is spheroidize annealed and coated with conventional forming materials, then a precision mandrel is used to back extrude helical gear teeth into the workpiece using a hydraulic press and specialized tooling. In this way, helical gear teeth 84, shown in
The park brake teeth 142 are cold formed or hob cut on the outer surface 188 of the drum portion 132, where its wall thickness is increased along a length of the drum portion as shown in
Spline 138 is broached on the inner surface of the hub 136, thereby forming a drive connection that is engaged with a spline on the outer surface of the output shaft 140.
Finally, the integrated ring gear-park brake drum 130 is heat treated.
In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that the alternate embodiments can be practiced otherwise than as specifically illustrated and described.
Claims
1. A component for transmitting torque between a gear unit and a shaft, comprising:
- a ring gear portion;
- a park brake drum portion formed integrally with the ring gear portion;
- a disc portion formed integrally with the park brake drum portion; and
- a hub portion formed integrally with the disc portion.
2. The component of claim 1, wherein the ring gear includes internal helical gear teeth.
3. The component of claim 1, wherein the hub portion includes spline teeth directed axially along an axis and located on an inner surface of the hub portion facing the axis.
4. The component of claim 1, wherein the park brake drum portion includes series of park brake teeth extending along an axis at an axial end of the park brake drum portion.
5. The component of claim 1, wherein the park brake drum portion includes series of park brake teeth extending radially from an outer surface.
6. The component of claim 1, wherein a hub portion includes spline teeth directed axially along an axis and located on an outer surface of the hub portion facing away from the axis.
7. A component for transmitting torque between a planetary gear unit and a shaft, comprising:
- a park brake drum portion including, a surface that extends along an axis, and a series of park brake teeth mutually spaced about the axis and located on the surface;
- a disc portion formed integrally with the park brake drum portion and extending toward the axis; and
- a hub portion formed integrally with the disc portion, including a hollow cylinder that extends along the axis and spline teeth formed on the hollow cylinder.
8. The component of claim 7, wherein the spline teeth are directed axially along the axis and are located on an inner surface of the hub portion facing the axis.
9. The component of claim 7, wherein the park brake teeth are located at an axial end of the park brake drum portion.
10. The component of claim 7, wherein the park brake teeth extend radially from an outer surface of the park brake drum portion.
11. The component of claim 7, wherein spline teeth are directed axially along the axis and are located on an outer surface of the hub portion facing away from the axis.
12. A component for transmitting torque between a planetary gear unit and a shaft, comprising:
- a ring gear portion including an inner surface formed with gear teeth that extend angularly about and along an axis;
- a drum portion formed integrally with the ring gear portion and including a surface that extends along the axis;
- a disc portion formed integrally with the drum portion and extending toward the axis; and
- a hub portion formed integrally with the disc portion, the hub portion including a hollow cylinder that extends along the axis and spline teeth.
13. The component of claim 12, wherein the gear teeth are internal helical gear teeth.
14. The component of claim 12, wherein the spline teeth are directed axially along the axis and are located on an inner surface of the hub portion facing the axis.
15. The component of claim 12, wherein spline teeth are directed axially along the axis and are located on an outer surface of the hub portion facing away from the axis.
Type: Application
Filed: Oct 3, 2008
Publication Date: Apr 8, 2010
Inventors: Joseph Szuba (Dearbom, MI), Rodney G. Whitbeck (Northville, MI)
Application Number: 12/245,065
International Classification: F16H 57/10 (20060101);